The explosive adoption of video-enabled wireless mobile devices has triggered a significant increase in data traffic across wireless networks and exposed the capacity constraints of conventional wireless network topologies.
Conventional wireless network (e.g., cellular network) deployment requires careful planning to maximize frequency reuse, minimize coverage dead zones, and minimize inter-cell interference. Wireless network deployment is labor intensive due to a significant amount of measurements and field trials. To reduce the cost of deployment, many network operators deploy macro cells which provide larger coverage footprint and higher capacity. This approach can work when the subscribers' service types are mainly conversational (e.g., voice), interactive (e.g., web browsing and instant messaging), or low rate streaming. These are the typical service types for 2G (e.g., GSM) and early 3G (e.g., UMTS Release 99 and CDMA2000) cellular networks where macro cell can often provide adequate Quality of Service (QoS) to fulfill the majority of subscribers' needs.
More subscribers are demanding faster data service as the bit rate at the air interface increases with the advance of the wireless technology (e.g., 3.5G and 4G). One example of 4G networks is LTE (e.g., 3GPP Release 8 and beyond), another is WiMax (e.g., IEEE802.16e and beyond). Given the limited available spectrum, the capacity becomes a serious issue for conventional macro cell. The capacity issue has caused a shift in cellular network deployment paradigm from well partitioned large coverage macro cells to densely deployed smaller cells (e.g., picocell, remote radio head, and femtocell), many being added dynamically in non-fixed locations. A mix of such cells with a combination of different air interfaces is often termed as Heterogeneous Networks (HetNet).
Self-Organized Networks (SON) is a relatively new concept in wireless networks and are typically using self-configuration and self-healing with respect to macrocell networks. There exist critical shortcomings associated with the current realization of SON, such as an inability to realize SON between small cells and macrocells, an inability to manage interference, reuse spectrum, and various other shortcomings.